1. Field of the Invention
This invention relates to communicating systems in general and more particularly, to a communicating system in which security control words are exchanged between both parties in a two-way communications exchange and the communications security words are further used to control selective data exchange.
2. Description of the Prior Art
Security in a system in which multiple users have access to a common data bank or in which multiple users can communicate with each other has historically presented a problem. That is, it is extremely important that data contained in a data bank be only accessed or manipulated by those users which are authorized to do so.
Many prior art techniques have been utilized to prevent unauthorized access to a data bank or a terminal by an unauthorized user. One of the most common earlier techniques to prevent unauthorized access to data was a technique in which the user desiring access was required to key in an identifier code. This identifier code was then examined by the receiving party to determine whether access would be allowed. If the code were a proper code, automatic communications channels would then be set up for the sending and receiving of information between the requesting party and the receiving party. Thus, a one-way identification was required. Other variations of this technique included patch board wiring of terminals to provide a unique identifier code. This technique had a primary shortcoming in that the code could be obtained by examining the patch board or plug board wiring and could therefore be duplicated by a person seeking to break security of the system. This led to a more sophisticated technique in which the identifier code was hardwired in a manner such that visual examination would not yield the specific code. This type of system is described in U.S. Pat. No. 3,735,106 entitled "Programmable Code Selection for Automatic Address Answerback in a Terminal System" with John T. Holloway as inventor. However, in all of these systems above discussed, the security provided was only one-way in that once the receiving party had verified that the code was a proper identifier code, communications could be established. This is without consideration as to whether the particular party sending the code was actually authorized to use the code.
In addition, in heretofore known communications systems, communication codes which were sent were used almost exclusively to establish the communication link and no control of data accessing at all or other use of the security codes was contemplated.